Boreholes ahead of a water pocket must be drilled at least how many meters ahead of the face?

• A. 4 meters
• B. 6 meters
• C. 8 meters
• D. 10 meters

Answer: (C)

The idea is to pre-drain and isolate a water pocket before the face reaches it. Drilling boreholes ahead into the water-bearing zone provides an early warning and lowers water pressure, so you can pump, seal, or otherwise control the area before you advance.

Eight meters gives a practical safety margin: far enough to detect and begin management of the water pocket and allow protective actions to take effect, but not so far that it unduly slows advance. Closer distances provide less warning and may not relieve pressure effectively, while much longer distances add unnecessary delay. Therefore, eight meters is the minimum standard.